The objectives of this program are: (1) To study the genetic regulation of cell malignancy by producing hybrids between malignant rodent and nonmalignant human cells as well as between malignant and nonmalignant human cells, the latter with appropriate marker chromosomes, and then determine if a specific chromosome or chromosomes of the nonmalignant partner will suppress the malignant characteristics of the tumor cells. (2) To transfer small amounts of genetic information from donor to recipient cells in order to develop cell systems for clarifying the mechanism by which mammalian cells regulate gene activity. BIBLIOGRAPHIC REFERENCES: Freedman, V.H., Brown, A.L., Klinger, H.P. and Shin, S.I.: Mass production of animal cells in nude mice with retention of cell specific markers. Exp. Cell Res. 98:143-151 (1976). Klinger, H.P. and Glasser, M.: Correlation of maternal contraceptive history with chromosomes, sex ratio and anthropometric measurements of the fetus and neonate. pp. 27-43. In: Population Cytogenetics, E.B. Hook and I.H. Porter, eds. Academic Press, New York, 1977.